The present disclosure relates to a sheet conveyance mechanism that conveys sheets such as a paper sheet and the like, a document conveyance apparatus, and an image forming apparatus including the sheet conveyance mechanism.
In image forming apparatuses such as a facsimile, a copy machine, a printer and the like, sheet conveyance mechanisms, which include a feeding portion having a drive roller, are widely used as devices for conveying sheets such as a paper sheet, a cloth, a sheet for an OHP and the like.
Such a sheet conveyance mechanism includes: a feeding portion that has a drive roller; a detection sensor that is disposed in a downstream side of the feeding portion in a sheet conveyance direction and detects presence of a sheet; and a pair of oblique movement sensors that detect am oblique movement of a sheet. The pair of oblique movement sensors are disposed at positions away from each other by a predetermined interval in a direction intersecting the sheet conveyance direction. And, in a case where after one oblique movement sensor detects a front end portion of a sheet, the other oblique movement sensor does not detect the front end portion of the sheet by a time when a predetermined period elapses, it is determined that the sheet is oblique by a predetermined angle or more and rotation of the drive roller is stopped.
Besides, a sheet conveyance mechanism is known which is able to detect an oblique movement of a sheet by means of one detection sensor and one oblique movement sensor. In this sheet conveyance mechanism, the detection sensor is disposed in a more upstream side than the oblique movement sensor in a sheet conveyance direction, and the detection sensor and the oblique movement sensor are disposed at positions away from each other by an interval in a direction intersecting the sheet conveyance direction. And, in a case where after the detection sensor detects a front end portion of a sheet, the oblique movement sensor does not detect the front end portion of the sheet by a time when a predetermined period (period that is required for the front end portion of the sheet to be conveyed between the detection sensor and the oblique movement sensor) elapses, it is determined that the sheet is oblique by a predetermined angle or more and the rotation of the drive roller is stopped.